Update readme

README.md

@@ -65,6 +65,10 @@ We would like to extend our thanks to the following sponsors for funding Laravel
 
 Thank you for considering contributing to the Laravel framework! The contribution guide can be found in the [Laravel documentation](https://laravel.com/docs/contributions).
 
+## Code of Conduct
+
+In order to ensure that the Laravel community is welcoming to all, please review and abide by the [Code of Conduct](https://laravel.com/docs/contributions#code-of-conduct).
+
 ## Security Vulnerabilities
 
 If you discover a security vulnerability within Laravel, please send an e-mail to Taylor Otwell via [[email protected]](mailto:[email protected]). All security vulnerabilities will be promptly addressed.